When using hand-held, electrically or pneumatically driven tools different sockets, or sleeves, can be attached to the driving, output shaft of the tool so that the tool is able to perform different kinds of work. In order to enable a socket to be fitted quickly to the output shaft of the tool, the tool shaft has been given a substantially square cross-sectional shape, such as the form of a square peg, and the socket has been provided with a corresponding square hole. In order to enable the socket to be connected detachably to the tool shaft, the shaft has been provided with one or more spring-operated locking balls which are pressed into holes in the shaft when the socket is pressed onto the shaft. The balls then fixate the socket, by being pressed-out, under the action of a spring force, into grooves or the like provided in the socket, when the socket is positioned correctly on the shaft. The socket can be fitted to and removed from the hand-held tool manually. The socket is first aligned with the tool shaft and then pressed onto the shaft. Subsequent to using the socket, or when wishing to replace the socket with another, the socket is pulled sharply and forcibly away from the shaft.